1201.4385
Prograde and regrograde black holes: whose jet is more powerful?
Tchekhovskoy, McKinney
Study prograde and retrograde disc accretion on rapidly spinning BHs via global 3d time-dependent non-radiative GR magnetohydrodynamic simulations. Discs contain more large-scale vertical magnetic flux than the accreting gas can push into the BH; BH becomes saturated with flux, and strong centrally concentrated large-scale magnetic fields form that obsstruct the accretion and lead to a magnetically arrested disk. Show that the efficiency with which such accretion systems generate steady outflows depends only on the dimensionless BH spin a, and accretion disk angular thickness h/r. Prograde BHs with thick discs generate jets and outflows several times more efficiently than retrograde BHs, for the same absolute value of spin. Both orientations can reach high values of outflow efficiency, eta~100%, with higher efficiency values for thicker discs.
1201.4386
The assembly history of disk galaxies: II. Probing the emerging Tully-Fisher relation during 1<z<1.7
Miller, Ellis, Sullivan, Bundy, Newman, Treu
New measurements of the resolved spectra of 70 morphologically-selected star-forming galaxies with i_AB<24.1 in the redshift range 1<z<1.7. Using ACS images, successfully recover rotation curves using the extended emission line distribution of OII to 2.2 times the disk scale radius for a sample of 42 galaxies. Combining these measures with stellar masses derived from HST and ground-based near-infrared photometry enables constructing the stellar mass Tully-Fisher relation in the time interval between z~1 and z>2. Find a well-defined TF relation with up to 60% increase in scatter and only a modest zero-point shift, Delta M* -0.06pm0.02 dex at z~1.7, compared to local observation. Sample is incomplete. Discuss implicaton of typical SF disk galaxies evolve to arrive on a well-defined TF relation with a short period of cosmic history.
1201.4387
The stellar IMF, core mass function, and the last-crossing distribution
Hopkins
Derive stellar IMF as a consequence of turbulent density fluctuations, using an argument similar to Press Schechter 1974 for Gaussian random fields. This solution does not resolve the 'cloud in cloud' problem, nor does it extend to large scales that dominate the velocity/density fluctuations. In principle, these can change the results at the order-of-magnitude level. Here, use results from Hopkins 2011 to generalize the excursion set formalism and derive the exact solution in this regime. Argue that the stellar IMF and core mass function (CMF) should be associated with the last-crossing distribution; i.e., the mass spectrum of bound objects defined on the smallest scale on which they are self-gravitating. This differens from the first-crossing distribution (mass function on the largest self-gravitating scale) which si defined cosmologically and which H11 show corresponds to the GMC mass function in disks. Derive an analytic equation for the last-crossing distribution that can be used for an arbitrary collapse threshold in ISM and cosmological studies. Show that the same model that predicts the GMC mass function and large-scale structure of galaxy disks also predicts the CMF (and by extrapolation IMF) in good agreement with observations. The only adjustable parameter in the model is the turbulent velocity power spectrum, which in the range p~5/3-2 gives similar results. Also use this to justify why the approximate solution in HC08 is reasonable (up to a normalization) over the CMF/IMF mass range; however there are significant corrections at intermediate and high masses. Discuss how the exact solution here can be embedded into time-dependent models that follow density fluctuations, fragmentation, successive generations of star formation.
1201.4394
Enhanced star formation rates in AGN hosts with respect to inactive galaxies from PEP-Herschel observations
Santini, et al
Compare average SF activity in x-ray selected AGN hosts with mass-matched control inactive galaxies, including SF and quiescent sources, at 0.5<z<2.5. Recent observations carried out by Herschel in GOODS-S, GOODS-N and COSMOS allow unbiased estimate of the far-IR luminosity, and hence the SF properties of the two samples. Accurate AGN host stellar masses are measured by decomposing their total emission into the stellar and nuclear components. Find a higher average SF activity in AGN hosts with respect to non-AGNs. The level of SF enhancement is modest (~0.26 dex at 3 sigma) at low X-ray luminosities, and more pronounced (0.56 dex) in the hosts of luminous AGNs. However, when comparing to SF galaxies only, AGN hosts are broadly consistent with the locus of their 'main sequence'. Investigate the relative far-IR luminosity distributions on active and inactive galaxies, and find a higher fraction of PACS detected, hence normal and highly SF systems among AGN hosts. Although different interpretation are possible, explain the findings as a consequence of a twofold AGN growth path: (1) faint AGNs evolve through secular processes, with instantaneous AGN accretion not thighly linked to the current total SF in the host galaxy, while the luminous AGNs co-evolve with their hosts through periods of enhanced AGN activity and SF, possibly through major mergers. An increased SF activity with respect to in active galaxies of similar mass is expected in the latter. The modeslt SF offsets measured in low lum. AGN hosts either (a) generated by non-synchronous accretion and SF histories in a merger scenario, or (b) due to possible connections between instantaneous SF and accretion that can be induced by smaller scale (non-major merger) mechanisms. Far IR luminosity distributions favour the latter scenario.
1201.4398
Reconstructing the near-IR BG fluctuations from known galaxy populations using multiband measurements of luminosity functions
Helgason, Ricotti,, Kashlinsky
Model fluctuations in the CIB arising from known galaxy populations using 230 measuremd UV, optical and NIR luminosity functions from a variety of surveys spanning a wide range of redshifts. Compare best-fit Schechter parameters across the literature and find clear indication of evolution with redshift. Provide fitting ofmulae for the multi-band evolution of the LFs; calculate the total emission redshifted into the near-IR bands in the observer frame and recover the galaxy number counts in the 0.45-4.5 micron range. Empirical approach in conjunction witha a halo model describing the clustering of galaxies allows computation of fluctuations of the unresolved CIB and compare the models to current measurements. Find that fluctuations from known galaxy populations are unable to account for more than 20 % of CIB clustering signal seen in Spitzer and AKARI at angular scales out to at least 5 arcmin. This holds true even if the LFs are extrapolated with the steepest faint-end slope allowed by data out to faint magnitudes. A rapid increase in the number of low-z dwarf galaxies just beyond the detection thresholds of current surveys would violate the shot noise levels seen in the data. Also show that removing resolved sources to progressively fainter magnitude limits isolates CIB fluctuations arising from higher z. This approach suggests that known galaxy populations are not responsible for the bulk of the fluctuation signal seen in the measurements.
1201.4401
What makes a galaxy radio-loud?
Ortega-Minakata, et al
* LINER: low-ionization nuclear emission-line region (O, O+, N+, S+). AGN or SF region emission, unknown. LINERs often referred to as AGN.
* Quasar: powered by an accretion disk around a SMBH of a galactic nucleus.
Compare SED of radio-loud and radio-quiet AGNs in 3 different samples observed with SDSS: RLAGNs, LLAGNs (low-luminosity) and IG-AGNs (isolated galaxies). All have similar optical spectral characteristics. Median SED of RLAGNs is consistent with the characteristic SED of quasars, while that of the LL AGNs and IG-AGNs are consistent with the SED of LINERs, with a low luminosity in the IG-AGNs than LL AGNs. Infer the masses of the BHs from the bulge masses: increase from the IG-AGN to LLAGNs are highest for the LR AGNs. All AGNs show accretion rates near or slightly below 10% of the Eddington limit, the differences in luminosity being solely due to different BH masses. Results suggests there are two types of AGNs, radio quiet and radio loud, differing only by the mass of their bulges or BHs.
1201.4405
Probing the intergalactic magnetic field with the anisotropy of the extragalactic gamma-ray background
Venters, Pavlidou
THe IGMF may leave in imprint on the anisotropy properties of the extragalactic gamma-ray background through its effect on EM cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will defect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thus inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Present a simple calculation of the magnitude of this effect; demonstrate that the two extreme cases (zero IGMF and IGMF strong enough to completely isotropize cascade photons) would be separable by ten years of Fermi observations and reasonable model parameters for the gamma-ray background. The anisotropy energy spectrum of Fermi gamma-ray BG could thus be used as a probe of the IGMF strength.
1201.4527
Gaussianizing the non-Gaussian lensing convergence field II: the applicability to noisy data
Yu, Zhang, Lin, Cui, Fry
A local monotonic Gaussian transformation can significantly reduce non-Gaussianity in noise-free lensing convergence field--promising for high-order lensing statistics. Present study of its applicability in lensing data analysis, in particular when shape measurement noise is present(ed) in lensing convergence maps. (1) shape measurement noise significantly degrades the gaussianization performance and the degradation increases for shallower surveys. (2) Wiener filter is efficient to reduce the impact of shape measurement noise. Gaussianization of the Wiener filtered lensing maps is able to suppress skewness, kurtosis ... by factor of 10 or more. Also works efficiently to reduce the bispectrum well to zero.
1201.4600
The evolution of stellar velocity dispersion during dissipationless galaxy mergers
Stickly Canalizo
Study the evolution of central stellar velocity dispersion (sigma) during dissipationless binary mergers of galaxies in N-body simulations. Sigma measured using the mass-weighting method, as well as flux-weighting method (similar to observations). Toy model for dust attenuation introduced in order to study the effect of dust attenuation on measurements of sigma. Find there are 3 stages in evolution: oscillation, phase mixing, and dynamical equilibrium. During the oscillation stage, sigma undergoes damped oscillations of increasing frequency. Amplitude of variation in sigma is smaller and more chaotic (mixing stage). Upon reaching dynamical equilibrium, sigma assumes a stable value. Use data on evolution of sigma to characterize the scatter inherent in making measurements of sigma in non-quiescent systems. Find: sigma does not fall below 70% or exceed 200% of its final quiescent value during merger, and that a random measurement of sigma in such a system is much more likely to fall near the equilibrium value than near an extremum. Toy model of dust attenuation suggested that dust can systematically reduce observational measurements of sigma and increase the scatter in sigma measurements.
1201.4752
A new third-order cosmic shear statistics: separating E/B-mode correlations on a finite interval
Krause, Scneider, EIfler
Decompose shear signal into E- and B- modes separately (without leakage of modes into each other) has been a long-standing problem in WL. At the 2-pt level, this was resolved by the ring statistics, and later COSEBIs; however, extending these concepts to the 3-pt level is not trivial. Currently used methods to decompose 3pt shear correlation functions into E- and B- modes require knowledge of 3PCF down to arbitrary small scales. Implies that the 3PCF needs to be modeled on scales smaller than the minimum separation of 2 galaxies and subsequently will be biased towards the model, or in the absence of a model, the statistics is affected by E/B-mode leakage (mixing). Derive a new 3rd order E/B-mode statistic that performs the decomposition using the 3PCF only on a finite interval, and therby is free of any E/B mode leakage while at the same time relying solely on information from the data. In addition, relate this 3rd order ring statistics to the convergence field, thereby enabling a fast and convenient calculation of this statistic from numerical simulations. Note: new statistics should be applicable to corresponding E/B-mode separation problems in the CMB polarization field.
1201.4773
THe dust emission of high-z quasars
Leipski, Meisenheimer
Detection of powerful near-IR emission in high-z (z>5) quasars: demonstrates that very hot dust is present close to the active nucleus. Currently being investigated. (T~65K is "unusually high temperature").
1201.4820
First light: a brief review
Wise
The first stars in the universe are thought to be massive, forming in DM haloes with masses around 1e6 solar masses. Recent simulations suggest that these metal-free (Pop III) stars may form in binary or multiple systems. Because of their high stellar masses and small host haloes, their feedback ionizes the surrounding 3kpc of intergalactic medium and drives the majority of the gas from the potential well. The next generation of stars then must form in this gas-poor environment, creating the first galaxies that produce the majority of ionizing radiation during cosmic reionization. Review the latest developments in the field of Pop III star formation and feedback and its impact on galaxy formation prior to reionization. Focus on the numerical simulations that have demonstrated this sequence of events, ultimately leading to cosmic reionization.
1201.4827
Evidence for quadratic tidal tensor bias from the halo bispectrum
Baldauf, Seljak, Desjacques, McDonald
Bias: relation between clustering properties of luminous matter (galaxies) and underlying DM distribution: important in interpreting galaxy surveys. Local bias model: galaxy density is a function of local matter density, infer the matter power spectrum or correlation function from the measured galaxy counterparts. However, gravitational evolution generates a term quadratic in the tidal tensor and thus non-local in the density field, even if this term is absent in the initial conditions (Lagrangian space). Because the term is quadratic, it contributes as a loop correction to the power spectrum, so the standard linear bias picture still apples on large scales, however, it contributes at leading order to the bispectrum for which it is significant on all scales. Such a term could also be present in Lagrangian space if halo formation were influenced by the tidal field. Measure the corresponding coupling strengths from the matter-matter-halo bispectrum in numerical simulations and find a non-vanishing coefficient for the tidal tensor term. Find no scale dependence of the bias parameters up to k=-0.1h/Mpc and that the tidal effect is increasing with halo mass. While the lagrangian bias picture is a better description of the results than the Eulerian bias picture, our results suggest that there might be a tidal tensor bias already in the initial conditions. Find that the coefficients of the quadratic density term deviate quite strongly from the theoretical predictions based on the spherical collapse model and a universal mass function. Both quadratic density and tidal tensor bias terms must be included in the modeling of galaxy clustering of current and future surveys if one wants to achieve the high precision cosmology promise of these datasets.
1201.4119
The intracluster magnetic field power spectrum in A2199
Vacca, et al
Investigate the magnetic field power spectrum in the cool core galaxy cluster A2199 by analyzing the polarized emission of the central radio source 3C338. The polarized radiation from the radio emitting plasma is modified by the Faraday rotation as it passes through the magneto-ionic intracluster medium. Use VLA observations to produce detailed Faraday rotation measure and fractional polarization images of the radio galaxy. Simulate Gaussian random 3-dimensional magnetic field models with different power-law power spectra and assume that the field strength decreases radially with the thermal gas density as n_e^eta. Comparing the synthetic and observed image, constrain the strength and structure of the magnetic field associated with the ICM. Find the Faraday rotation is consistent with magnetic field power law characterized by index n=2.8 pm 1.3 with a min and max fluctuation scale of 0.7 and 35 kpc. By including the modeling X-ray cavities coincident with the radio galaxy lobes, find a magnetic field strength of <B>=11.7 micro Gauss at the cluster center. Further out, the field decreases with the radius following the gas density to the power of eta=0.9.
1201.4125
Continuum reverberation mapping in a z=1.41 radio-loud quasar
Goicoechea, Shalyapin, Gil-Merino, Braga
* Reverberation (or echo) mapping: a time-domain technique to resolve the accretion flow in AGNs. Relies on the analysis of time-delayed responses of different emitting regions to original fluctuations in an irradiating source.
Q0957+561: the first discovered gravitationally lensed quasar. The mirage shows two images of a radio-loud quasar at redshift z=1.41. The time lag between these two images is well established around one year. Detect a very prominent variation in the optical brightness of Q0957+561A at the beginning of 2009, allowing prediction of presence of significant intrinsic variation in multi-wavelength light curves of the B image over the first semester of 2010. To study the predicted brightness fluctuations of the B image, conducted X-ray, NUV, optical and NIR monitoring campaign using both ground-based and space-based facilities. The continuum NUV-optical light curves revealed evidence of a centrally irradiated, standard accretion disk. Focus on the radial structure of the standard accretion disk and the nature of the central irradiating source in the distant radio-loud AGN.
The intracluster magnetic field power spectrum in A2199
Vacca, et al
Investigate the magnetic field power spectrum in the cool core galaxy cluster A2199 by analyzing the polarized emission of the central radio source 3C338. The polarized radiation from the radio emitting plasma is modified by the Faraday rotation as it passes through the magneto-ionic intracluster medium. Use VLA observations to produce detailed Faraday rotation measure and fractional polarization images of the radio galaxy. Simulate Gaussian random 3-dimensional magnetic field models with different power-law power spectra and assume that the field strength decreases radially with the thermal gas density as n_e^eta. Comparing the synthetic and observed image, constrain the strength and structure of the magnetic field associated with the ICM. Find the Faraday rotation is consistent with magnetic field power law characterized by index n=2.8 pm 1.3 with a min and max fluctuation scale of 0.7 and 35 kpc. By including the modeling X-ray cavities coincident with the radio galaxy lobes, find a magnetic field strength of <B>=11.7 micro Gauss at the cluster center. Further out, the field decreases with the radius following the gas density to the power of eta=0.9.
1201.4125
Continuum reverberation mapping in a z=1.41 radio-loud quasar
Goicoechea, Shalyapin, Gil-Merino, Braga
* Reverberation (or echo) mapping: a time-domain technique to resolve the accretion flow in AGNs. Relies on the analysis of time-delayed responses of different emitting regions to original fluctuations in an irradiating source.
Q0957+561: the first discovered gravitationally lensed quasar. The mirage shows two images of a radio-loud quasar at redshift z=1.41. The time lag between these two images is well established around one year. Detect a very prominent variation in the optical brightness of Q0957+561A at the beginning of 2009, allowing prediction of presence of significant intrinsic variation in multi-wavelength light curves of the B image over the first semester of 2010. To study the predicted brightness fluctuations of the B image, conducted X-ray, NUV, optical and NIR monitoring campaign using both ground-based and space-based facilities. The continuum NUV-optical light curves revealed evidence of a centrally irradiated, standard accretion disk. Focus on the radial structure of the standard accretion disk and the nature of the central irradiating source in the distant radio-loud AGN.
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